4S_Paper_TET_Rhodos_080526

8/2/2019 4S_Paper_TET_Rhodos_080526

http://slidepdf.com/reader/full/4spapertetrhodos080526 1/11

TET-1

A GERMAN MICROSATELLITE FOR ON-ORBIT-VERFICATION

Stefan Föckersperger(1), Klaus Lattner(1), Clemens Kaiser(1), Silke Eckert(2), Wolfgang Bärwald(2),

Swen Ritzmann(2), Peter Mühlbauer(3), Michael Turk(4), Philipp Willlemsen (4),

(1)Kayser-Threde GmbH, Wolfratshauser Straße 48, 81379 München, Germany,

Email: [email protected](2) Astro- und Feinwerktechnik GmbH, Albert-Einstein-Straße 12, 12489 Berlin, Germany,

Email: [email protected]

Deutsches Zentrum für Luft-und Raumfahrt e.V. (DLR), Rutherfordstr. 2, 12489 Berlin

E-Mail: [email protected]

(3) Deutsches Zentrum für Luft- und Raumfahrt e.V. (DLR), 82234 Weßling, Germany,

Email: [email protected]

(4) DLR Space Agency,Königswinterer Straße 522-524, 53227 Bonn, Germany,

E-Mail: [email protected]

ABSTRACT

Due to the high safety standards in the space industry

every new product must go through a verification

process before qualifying for operation in a space

system. Within the verification process the payload

undergoes a series of tests which prove that it is in

accordance with mission requirements in terms of

function, reliability and safety. Important verification

components are the qualification for use on the ground

as well as the On-Orbit Verification (OOV), i.e. proof that the product is suitable for use under virtual space

conditions (on-orbit). Here it is demonstrated that theproduct functions under conditions which cannot or can

only be partially simulated on the ground.

The OOV-Program of the DLR serves to bridge the gap

between the product tested and qualified on the ground

and the utilization of the product in space. Due to

regular and short-term availability of flight

opportunities industry and research facilities can verify

their latest products under space conditions and

demonstrate their reliability and marketability.

The Technologie-Erprobungs-Träger TET (Technology

Experiments Carrier) comprises the core elements of theOOV Program. A programmatic requirement of the

OOV Program is that a satellite bus already verified in

orbit be used in the first segment of the program. An

analysis of suitable satellite buses showed that a

realization of the TET satellite bus based on the BIRDsatellite bus fulfilled the programmatic requirements

best.

Kayser-Threde was selected by DLR as Prime

Contractor to perform the project together with its major

subcontractors Astro- und Feinwerktechnik, Berlin for

the platform development and DLR-GSOC for the

ground segment development. TET is now designed tobe a modular and flexible micro-satellite for any orbit

between 450 and 850 km altitude and inclination

between 53° and SSO. With an overall mass of 120 kg

TET is able to accommodate experiments of up to 50

kg. A multipurpose payload supply system under

Kayser-Threde responsibility provides the necessary

interfaces to the experiments. The first TET mission is

scheduled for mid of 2010. TET will be launched as

piggy-back payload on any available launcher

worldwide to reduce launch cost and provide maximum

flexibility. Finally, TET will provide all servicesrequired by the experimenters for a one year mission

operation to perform a successful OOV-mission with its

technology experiments leading to an efficient access tospace for German industry and institutions.

1. BACKGROUND

The goal of the OOV (On-Orbit-Verification)-Program

is to qualify new technological solutions for their

application in space projects. It focuses on the in-flight

demonstration and verification of highly advanced

technologies. The core element of the program is the

micro-satellite TET (Technology Experiment Carrier) asa platform for the verification flight.

1.1 The need for on-orbit verification

It is necessary to validate new, unproved techniques and

technologies before using them in advanced missions.The OOV-Program fills the gap between a technology

which has been qualified on the ground and its

application in space. In order to support German

industry and research institutes, the German Space

Agency provides flight opportunities to qualify in-flight



new technological solutions in all areas of space craft

technology such as power generation and storage,

propulsion, guidance, navigation and control.

The first part of the program is scheduled for the years

2005-2012. The overall budget of the program within

this time span is about 34 M€. The program isconducted in cooperation with DLR Space Research

(PD-W).

1.2. Flight opportunities

Flight opportunities for technology demonstration and

verification should ideally be provided on a regular

basis, independent, cost efficient and safe. A market

survey of German industries’ and institutes’

technologies has shown that about 75 % of the

experiments can be verified using a micro-satellite.

The OOV-Program is thus structured into two main

parts with respect to the flight opportunities offered.

The first comprises the micro-satellites TET with a

planned flight every two years. For payloads which do

not fit on TET, the DLR Space Agency cooperates with

national and international partners in order to provide

flight opportunities on other carriers.

2. MISSION OVERVIEW

The whole mission is designed based on the mainmission requirements shown in Tab.1.

Table 1: TET main mission requirementsMission duration: 1 month LEOP incl. Satellite

commissioning and 12 months mission operations

Type of Orbit: circular

Orbit height: between 450 – 850 km

Orbit inclination: 53° to sun-synchronous

Piggy-Back Launch

Reliability requirement: 0.9 (for platform and payload support

system)

Ground stations: Weilheim for TT&C, Neustrelitz for payload

data downlink

TET platform should be based on the BIRD satellite

(maximum use of the BIRD heritage)

TET-1 Satellite mass: 120kg

Total Payload mass: 50kg

Derived from the above mentioned requirements and

following a detailed mission analysis a mission scenario

has been defined as shown in Fig. 1 below. The TET-1

satellite is launched as piggy-back in a LEO orbit. After

LEOP and Commissioning the one year mission

operation is controlled via the mission control centre in

Oberpfaffenhofen. Payload data are stored in the

payload data centre in Neustrelitz and can be retrieved

from the Experimenters via secured web access.

GSOC / Oberpfaffenhofen

DLR groundstation Weilheim

Planning Mission Control

Legend:Data Transfer

Requests

Command & Control

Experimenters

TET-1Mission

Orbit Launch

DLR groundstation & PDC Neustrelitz

e.g. SOYUZ

Figure 1: TET Mission Scenario

The essential conditions for operation of the payload

are:

- Electrical power supplied by the satellite bus to the

single experiment,- Thermal power consumption of the payload

impacts the overall thermal system,

- Pointing mode of the satellite,

- Data take/rate of the experiment limited by the

mass memory.

A careful mission planning for the experiments is

necessary to be compatible with these conditions. The

following principle operational scenarios are foreseen:

- Standard weekly mission scenario: the TET

payload is operated according to a schedule that isrepeated after one week (approx. 15 orbits with

approx. 100 minutes data downlink every day).

- Mission scenario 12: 12 times per year continuous

experiments lasting 4 days are performed.

- Mission scenario 2: 2 times per year experiments

with direct space-ground link is foreseen lasting 2

days.

These operating scenarios are commanded from the

ground station and controlled by the Payload SupplySystem which is detailed in chapter 3.3.2.

The final decision concerning the piggy-back launcheris not jet made, but due to economical reasons a launch

opportunity with SOYUZ/FREGAT from Baikonur is

first choice. TET-1 is intended to be launched together

with a Russian weather satellite METEOR-2. The

adjoining picture shows a possible accommodation of

TET-1 on SOYUZ/FREGAT. The final orbit is a sun-

synchronous, 550km altitude, circular orbit. During

launch the satellite is inactive and after separation from

the launcher the satellite is activated.



Figure 2: TET-1 Accommodation on launcher

The overall mission comprises the following mission

phases.

Transport to Launch Site

Launch Campaign

Launch und Early Orbit Phase

Commissioning

Mission Operation

Disposal

Storage in case of Lauch D elay

Figure 3: TET-1 mission phases

The main phases are described in more details:

- LEOP: The Launch and Early Operations Phase

will last a few days and has the goal to ensure

satellite survival after separation from the launcher.

Solar arrays will be deployed; satellite attitude willbe stabilized to allow battery charging by the solar

arrays and initial housekeeping data will be

acquired from the LEOP ground station network.

LEOP will end when the satellite is in a stable

situation with respect to power, attitude and

communications.

- Bus and NVS commissioning: Components which

were not activated in LEOP will be activated. Allsubsystems of the satellite bus and the NVS will be

thoroughly tested.

- Operational mission: The operational mission willlast 12 months. Payload commissioning and

payload operations will be performed in this phase.

- End of operations (disposal): In this phase the

payloads will be switched off and passivation

measures will be performed for the bus and the

payloads.The TET-1 mission is structured as shown in Figure 4

and consists of three elements:

- the Space segment,

- the Ground segment and

- the Launch segment

Figure 4: TET-1 Mission Elements

Each of these elements has been designed in past project

phases and the results are shown in the forthcoming

chapters.

3. SPACE SEGMENT

3.1. Overview

The TET-1 Space Segment consists of the Satellite Bus

and the Payload. At an overall mass of about 118kg the

Payload including the Payload Supply System and

necessary support structures contributes with about

50kg. Fig. 5 below shows the Satellite Bus with

integrated Payload in the launch configuration where

the two solar panels on the left and right side are notdeployed. The overall height of the Satellite is less than

880mm with a width of approximately 550mm and a

depth of 650mm.

OOV

Programme

ExperimentersTET

Mission #1

Ground

segment

Space

segment

Satellite Platform

Mission Control Centre

Ground Stations

Payload Data Centre

Launch

segment

Launcher

Infrastructure

Ground Support

Equipment

TET 1 Payload

Payload Support System

Payload Segment

TET

Mission TBD

Additional Experiments

Experiment 1

Experiment n

LEOP Network

TT&C Stations

Launcher TT&C Stations

Integration Facilities

Launcher Control Centre

TET Experiments

Mission #1

Experiment 1

Experiment n

Payload Data Station



Figure 5 TET-1 Satellite (launch configuration)

In the deployed configuration as shown in Figure 6

below, the Payload Segment can be seen more clearly. It

is located on top of the Satellite Bus main structure with

the Payload Base Plate as the mechanical and thermal

interface.

Figure 6: TET-1 Satellite (deployed configuration)

To limit the development time and to reduce the projectrisk the TET-1 satellite bus is based on the heritage of

the BIRD satellite bus. The open satellite structure of

the BIRD concept allows for a flexible payload

accommodation which has been adapted for size and

mass to fulfil the TET-1 needs.

11 experiments have been selected by DLR for this first

TET mission. The experiments are developed by 11

different companies and institutions and comprise

newest technology to be demonstrated for usage in

space environment. The technical areas cover next

generation solar arrays, navigation equipment, batteries,

cameras, communication equipment, and satellite

propulsion system and computer hardware.

The Payload to Satellite Bus interface is realized and

managed by a modular Payload Supply System

developed by Kayser-Threde, allowing to be customized

with minimum effort to the experiment needs and

thereby reducing the effort for recurring missions.

Table 2: TET-1 Technical Data

TET-1 Technical Data

Dimensions : 880 mm x 550 mm x 650

mm (H x W x D) with about

90 liters of payload

compartment

Mass : Bus 70 kg

: Payload 50 kg

Number of experiments : 11

Stabilization : 3-axes

Pointing accuracy : 5 arcmin

Payload power consumption : max 20W continuous

Uplink rate : 4 kbit/s

Downlink rate : 2.2 Mbit/s high rate

Orbit : 550 km, SSO

Launch : Mid 2010

Mission duration : one year

3.2. Satellite Bus

The TET satellite bus can carry various adapted. It is a

micro satellite bus based on the successfully employedmicro satellite BIRD (Bi-spectral Infra-Red Detection).

On 22 October 2001 the micro satellite BIRD (Bi-

spectral Infra-Red Detection) was launched successfully

as secondary payload with the Indian rocket PSLV-C3

(Polar Satellite Launch Vehicle) into a circular sun-

synchronous orbit of 572 km height. The satellite was

designed, integrated and tested at DLR Berlin-

Adlershof. The mission goal testing new small satellitetechnologies in space was accomplished as well as

testing a new generation of infrared sensors combined

with a modified WAOSS camera (Wide-Angle

Optoelectronic Stereo Scanner). For the first time it was

demonstrated that the expansion of vegetation fires and

related flame temperatures can be detected with a

special payload on a micro satellite. [1]

During the required life expectancy of 12 months all

components worked correctly. For more than 80 months

BIRD has been successfully sending data to earth.

Payload

Segment



In contrast to BIRD a higher payload total mass of 50

kg in a bigger dimension of 460 x 460 x 428 mm³ is

available for the payloads that should be verified. The

Payload Segment contains, besides the experiments,satellite bus components which need a dimension of

approx. 100 x 275 x 220 mm³ for star cameras and

140 x 55 x 45 mm³ for magnetic field sensors(Figure 7 ).

Figure 7: Available Payload Volume within TET-1

The satellite bus offers the possibility of fixing a

payload panel above the central solar panel. Additional

solar cells can also be installed on a special area on the

central panel.

Figure 8: TET-1 Satellite Bus with Solar Cells and freespace to install Payload Panels

Some other basic features of the TET satellite bus are

the compact micro satellite structure with high

mechanical stability and stiffness and a cubic shape in

launch configuration with a dimension of 650 x 550 x

880 mm³ (envelope) (see Figure 9).

The TET satellite bus relays on a passive thermal

control system with radiators, heat pipes, MLI,

temperature sensors and contingency heaters.

Figure 9: Envelope of TET Satellite Bus

The Power Subsystem consists of Power Control and

Power Distribution Units, NiH2 cell battery stacks

including T-control and solar panels. The solar array

consists of 3 panels; one fixed body mounted middle

panel and 2 deployable side panels. The array is

equipped with 246 solar cells (triple junction GaAs,

efficiency 28%), with an electrical power of 220W

(maximum power point). The capacity of the battery is

240Ah, energy transfer is done by DET

(DirectEnergyTransfer).

The Spacecraft Bus Computer (SBC) controls allactivities of the satellite bus. The SBC receives, stores

and processes the commands, gathers and evaluates the

housekeeping data of all subsystems and controls the

telemetry. Furthermore it is also the attitude control

computer of TET. The SBC consists of 4 identical SBC

boards and watchdog circuits for failure detection and

recovery. The architecture of the redundant SBC boards

(nodes) is totally symmetric, that means, each of the

boards is able to execute all control tasks. One node (the

worker) is controlling the satellite while a second node

(supervisor) is supervising the correct operation of the

worker node. The two other node computers are sparecomponents and are disconnected. If an anomaly of the

worker node is detected by the supervisor node the

supervisor substitutes the worker and takes over the

control of the satellite. [2]

The Attitude and Orbit Control System (AOCS) consists

of two star sensors, two gyroscopes, two

magnetometers, 2 sets of sun sensors, 4 reaction wheels,a magnetic coil system. The attitude control system

provides a high degree of autonomy basing on a state-

space representation of the attitude estimation,



prediction and control, a real-time operation system

embedding the attitude control software and a

combination of the attitude control with an on-board

navigation system (see Fig. 10 and 13).

Figure 10: Scheme of the AOCS Interfaces

One of the most complicated tests during the

verification process of the TET satellite bus is the

testing of the Attitude and Orbit Control System.

Software-in-the-loop simulations and hardware-in-the

loop simulations are well established test methods, but

the best solution is real end-to-end test of the AOCS

with a corresponding test facility. Based on theexperiences with the BIRD AOCS test facility during

the last years and the AOCS requirements, Astro- und

Feinwerktechnik Adlershof GmbH has developed and

built a new test facility for the end-to-end verification of

the AOCS (see Fig. 11). [3]

The communication takes place using S-Band with high

bit rate (2,2 Mbit/s) and low bit rate. The transmitter and

receiver channels are redundant and can be switched to

all antennas. (see Fig. 12).

Figure 11: Components of the TET Satellite Bus

Figure 12: Scheme of the Communication System

The TET Satellite bus consists of three compact

segments. In the service segment a battery, reaction

wheels, the power control and distribution unit and laser

gyro are installed. The Satellite Board Computer and the

Payload Supply System are located in the electronicssegment. The modifiable payload platform is the link

between electronics segment and payload segment. In

the payload segment are the experiments and also

satellite bus components (star sensors, magnetic fieldsensors and antennas (low-gain and GPS) (see Figure

13).



Figure 13: Components of the TET Satellite Bus

3.3. Payload

3.3.1. TET-1 Payload Segment incl. Experiments As mentioned, 11 experiments are accommodated in theTET-1 satellite. The list of experiments is given below:

- three different types of next generation solar cells

including thin-layer technology

- Lithium Polymer Battery

- two GPS receiver systems

- sensor bus system

- pico satellite propulsion system

- infrared camera as follow-up of the BIRD camera

system

- Computer hardware

- RF communication system.

The accommodation of the experiments in the PayloadSegment is shown on the following two figures. The

accommodation has been driven by the various

experiments needs as e.g. viewing directions,

unobstructed view angles for antennas, heat dissipation,

etc.

Figure 14: Accommodation of Experiments (1)

Figure 15: Accommodation of Experiments (2)

The solar cell experiments have been accommodated on

the sun pointing side of TET-1 next to the Satellite Bus

solar arrays, as shown in the next figure.

Figure 16: Accommodation of Solar cell Experiments

The TET-1 Payload configuration data is summarized in

Tab. 4.

Table 3: Payload configuration data

TET-1 Payload Data

Dimensions : 428 mm x 460 mm x 460

mm (H x W x D)

Max. Payload Mass : 50 kg incl. mass of PayloadSupply System

Power consumption cont. : 0 – 20 W incl. Payload

Supply System

Power consumption max. : 160W limited in time and

occurrence

Supply Voltage : 18 – 24VDC

Current max. : 8A

TM Data Rate : 2.2 Mbit/s max.

Storage : 512 MByte

Heaters : 0 to 15W



3.3.2 Payload Supply System

Via the Payload Supply System the interface between

the Satellite Bus and the experiments is controlled. The

Payload Supply System provides therefore a fixed part

that interfaces to the Satellite Bus and a flexible part

that can easily be adjusted to the experiments needs.

Satellite Bus ExperimentsPayloadSupply

System

Figure 17: Payloads Supply System Interface

Based on this concept the Payload Supply System can

be separated into three different parts:- the power supplies responsible for the supply of the

experiments and the Payload Supply System itself

- the processor boards that are used to control all

Payload Supply System activities

- the I/O boards that provide the interfaces to the

experiments.

All these parts will be realized on several printed circuit

boards that will be connected via backplane. Theexperiments will be connected via front panel

connectors.

The Payload Supply System is accommodated inside the

Electronic Segment of the Satellite Bus next to theSatellite Bus Controller as shown in the figure below.

Figure 18: Accommodation of the Payloads Supply

System

A block diagram of the Payload Supply System is

shown in Fig. 19.

NVS Power

NVS Controller

NVS Power 4

NVS Prozessorboard A/B

Memory

T r a n c e i v e r

T r a n c e i v e r

Digital I/OFPGA

CPUserial IF

GPIO

SpacewireMemory IF

Analog I/O

7x RS-422 / 1x I²C

8 x Relais Cmnd.

5 x Relais-Status

24 x GPIO/DAC

12 x AD590

4 x PT1000

16 x Analog In

3 x Spacewire

N u t z l a s t e n

S B C D a t a I F

2x RS-422

Power Control

18..24V

S

B C P o w e r

4 x A D 5 9 0

18..24V

NVS Power 5

HK Voltage Measurementprimary / switched

Latch Relais

Latch Relaiscurrent limiter

breaker

current limiterbreaker

NVS Power 1


breaker

DC/DCconverter


breaker

DC/DCconverter

NVS Power 2

HK primary CurrentMeasurement


breaker

DC/DCconverter

DC/DCconverter

+/- 5VLatch Relaiscurrent limiter

breaker

NVS Power 3


breaker

DC/DCconverter

DC/DCconverter

HK secondary VoltageMeasurement

5V (NL17)

12V (NL2)


breaker

relais on

relais off

HK secondary VoltageMeasurement

+/- 5V

1 x PPS

18..24V


breaker 18..24V


breaker

1..4 (NL1, NL6, NL16, Heating)

1..4 (N4, NL7, NL15, N18)

2x sync. IF

1x PPS

Figure 19: Payload Supply System Diagram

The functions provided by the software executed on the

Payload Supply System processor cover the followingtasks:

- control of experiments with minimal built-in

processing logic

- acquisition of housekeeping data of the experiments

and the Payload Supply System itself

- acquisition of measurement data of the experiments

- temporary storage of all acquired measurement and

housekeeping data

- formatting and packaging of data according

CCSDS for downlink

- reception and execution of commands from the

Satellite Bus Controller- Control of Payload Supply System devices as

switches, circuit breakers, etc.

- management of thermal control of experiments and

Payload Supply System

- Boot, self-test and software update management

- Failure Detection, Isolation and Recovery,

redundancy management

Via the housekeeping sensors of the Payload Supply

System the software controls the heaters installed in the

Payload Segment to maintain the required temperatures

for operating the experiments.

Payload Supply

System



4. GROUND SEGMENT OVERVIEW

TET – Ground Segment Overview

Launch

Service

Provider

Launch

Service

Provider

11 Users / Experiments:2 GPS-TechExperiments3 New Generation Solar Cells

4 Space-BusExperiments1 BatteryTechnology1 IR-Camera (BIRD-heritage)

11 Users / Experiments:2 GPS-TechExperiments3 New Generation Solar Cells4 Space-BusExperiments

1 BatteryTechnology1 IR-Camera (BIRD-heritage)

PayloadData CenterNeustrelitz

DFD-BN

Payload DataCenterNeustrelitz

DFD-BN

Neustrelitz

O‘Higgins

(Antarctica)

German RemoteSensingData Center

DFD-BI

CSA -CanadianSpace Agency

CSA -Canadian

Space Agency

SKT, SHB (Canada)

Weilheim

German Space OperationsCenter

GSOC

FlightDynamics

FlightOperations & Management

Communications

& GroundStations

LEOP and Routine Operations

Launchand Early Orbit Phase only

Figure 20: TET Ground-Segment Overview

Ground Segment project management, integration, test

and training as well as all LEOP activities, routinemission operation and satellite control will be

performed at the German Space Operations Center

(GSOC).

Interfaces are established to the German Remote-

Sensing Data Center (DLR-internal) and to external

partners such as the launch-provider (data-exchange)

and to the Canadian Space Agency (CSA) as provider of

additional ground-station for LEOP-support. This isdone on a co-operative basis (no exchange of funds), as

DLR-GSOC supports Canadian missions with its

resources.

DLR-owned S-Band ground stations in Weilheim,

Neustrelitz and O’Higgins/Antarctica (for LEOP only)provide the necessary access to the satellite in all

mission phases.

This ground station concept based mainly on DLR-

owned resources is one of the reasons for cost-effective

project design. However, operational requirements

sometimes need to be tailored to the available uplink-

and downlink resources.

A so called Payload Data Center (PDC) will be

provided at the location of the data reception station in

Neustrelitz. The main tasks are acquisition, extraction,

processing (formatting to a generic ASCII format)

archiving and provision of payload data.

The 11 users with their experiments onboard TET-1retrieve (download) their data via a secure FTP

interface. The main goals for the design andimplementation process of the Ground Segment can be

summarized as follows:

- Minimize number of project-specific systems and

tools

- Make use of multi-mission core systems (Mission

Data System, Flight Dynamics, networks,…)

- Use of multi-mission documentation and combining

documents reasonably

- Efficient pooling of multi-project resources and

personnel

Figure 21: TET Ground Segment Functional Structure

and Interfaces

Above figure illustrates the main functions of the

ground-segment and their interfaces. The core element –

the so-called Mission Data System (MDS) – is already

fully operational and available and just needs to be

configured for TET. The only exception being the

Mission Information Base (MIB) which is specific for

each project as it contains the definitions of TM and TC.

5. MISSION OPERATIONS

For the TET-1 mission the ground-segment will

basically provide the execution of all necessary

activities for a sound operation of the space segmentand a continuous survey (Monitoring & Control) of

functionality and integrity of all project elements. DLR-

GSOC will perform this for all mission phases after

launch for both the space segment and the ground

segment.

During the mission preparation phase detailed analysis

and planning of the mission operation will be

undertaken and the operations processes will be

designed, implemented, tested and validated. In the

LEOP, bus commissioning- and routine operations

phase telemetry data of the satellite and payload status

is received and processed and telecommands for

controlled changes of the satellite are sent. Onboard

power and data storage availability, S/C attitude andpayload requirements for previously scheduled payload

events are compiled and executed.

In preparation for this, training sessions will be

performed during project-phase D for all operations

personnel at DLR/GSOC. The training comprises of

class room and simulation sessions.

Due to the BIRD-heritage, the operational ground

processes are already largely known to the experienced

operations personnel at the control center GSOC and at

the PDC in Neustrelitz.



TET – Ground Station Network and orbital injection

LEOP: LEOP and Routine:

Saskatoon(CSA) St. Hubert (CSA) Neustrelitz (DLR-DFD)

O‘H iggins (D LR -D FD ) Wei lheim (DLR-GSOC , 2 x TM/TC )

Figure 22: TET-1 Ground-Station Coverage and Orbit

Tracks

After launch and successful orbit-injection andseparation of TET from the launcher, GSOC is

responsible for execution of early orbit operations.

Above figure illustrates the first orbits after launch and

the related coverage zones by the available ground-

stations. LEOP is characterized as follows:

- Launch from Baikonour with Soyuz as secondary

payload (“piggy-back”)

- Separation from Fregat upper-stage after injection

in desired orbital altitude. Separation location is still

TBD

- Spacecraft initiates automatic activation sequence

and transits to safe-mode (attitude, power, thermal,communication)

- Initial acquisition of signal over DLRs O‘Higgins

(Antarctica) or Weilheim (Germany) ground-

stations

- Begin of orbit determination process utilizing

tracking data gained from the ground-station in

Weilheim respectively from the external LEOP -

support stations

- Start of checkout and ground-commanded

configuration activities

- Support by 2 Canadian ground-stations begins after

4 orbits

- LEOP and bus commissioning duration: 7 days- followed by activation of payloads and their

checkout

- The routine mission operation and satellite control

will be performed by GSOC engineering personnel

during normal working hours with the support of a

multi mission flight operations team (MMFS-team)

responsible for shift operations as required. Three

different pre-defined operational scenarios are

identified to the present:

- General activities on a weekly basis,

- Additional activities during 4 days once per month,

- Specific activities during 2 days at start and end of

mission.

Routine operation is characterized as follows:

- Ops-planning, health-monitoring and onboardmaintenance at GSOC

- Upload of time-tagged executable commands to bus

and payload: 3 days in advance, weekly cycle

- Commanding and TM-reception: once per day via

Weilheim ground-station- Upload of S/W and maintenance on request

- Download of data (payload and bus): 4 times per

day

- Data reception and processing at Payload Data

Center: automatic, 7 days a week

Operational tasks and responsibilities within the ground-

segment during mission conduct:

- The DLR ground station in Weilheim will serve as

main uplink (TC) and housekeeping telemetry

reception (HK-TM) station.

- The DLR ground station in Neustrelitz will be used

as main downlink station for payload data

- S-band data will be routed in real time from

Weilheim and Neustrelitz to the Operations Center

in Oberpfaffenhofen (GSOC) and all raw data will

be stored at the receiving ground-stations for a

limited period.

- Calibrated housekeeping data (i.e. uplink and

downlink) will be archived at DLR/GSOC and canbe used at GSOC for offline analysis, while payload

data will be formatted to an additional generic

ASCII format, provided and archived at Neustrelitz

together with the raw instrument sourcee packets

and other auxiliary data products

- Mission control, preparation and execution of

flight-operations, health-monitoring and

performance analysis is performed at GSOC, as

well as permanent orbit determination utilising

- GPS data and ‘station predicts’ will be generated to

support acquisition of the satellite by the ground-

stations.

- Initially, a dedicated control team consisting of engineers and spacecraft-operators will conduct

LEOP and the initial commissioning phase (1-3

weeks, depending on mission progress).

- A soon as spacecraft and experiment activation and

checkout are completed, all operations is transferred

to the multi-mission environment – this refers to the

control-facilities (consoles, control-room) as well as

the operations concept (monitoring and control

done by the Multi-Mission-Flight-Support-Team

under offline and on-call supervision by engineers).



The above outlined operations concept for TET based

on DLR-internal resources and on the multi-mission

approach will make the most efficient use of the

existing facilities, processes and teams as TET will beanother mission added to the pool of presently 5

satellites permanently operated at GSOC.

6. SERVICES AND PRODUCTS

All users with experiments onboard TET-1 will beprovided two payload data sets with different formats on

a ftp-server. The Payload Data Centre (PDC) processes

the received payload data during and immediately after

data reception, which is planned 4 times a day.

The products (instrument source packets in raw binary

form and as ASCII text file) will be made available at

the ftp server 15 min after finishing data reception,

secured by protected and selective access.

The format of both payload data products for all 11

users is identical, while contents differ of course.The user additionally receives all auxiliary data

(required for calibration purposes or additional

processing) provided by GSOC via the same interface.

All data is stored on a permanent archive and a function

for later retrieval is provided.

Table 4: TET Ground-Segment Data Products

One genericformat for allusers, contentsspecific.

User Specific(pass-wordprotectedaccess)

ASCIIConverted File

Generic format,but specificcontent foreach user


BinaryRaw InstrumentSource Packets(ISP)

PayloadData

variousNot restrictedASCII- Logs

Not restrictedASCII- Bus-HK-data(including NVS)

Not restrictedtbd- Attitude

Not restrictedtbd- Orbit

Not restrictedtbd- Ops-planningand as flown

AuxiliaryData

RemarkAvailabilityTypeContentDataProducts

One genericformat for allusers, contentsspecific.


ASCIIConverted File

Generic format,but specificcontent foreach user


BinaryRaw InstrumentSource Packets(ISP)

PayloadData

variousNot restrictedASCII- Logs

Not restrictedASCII- Bus-HK-data(including NVS)

Not restrictedtbd- Attitude

Not restrictedtbd- Orbit

Not restrictedtbd- Ops-planningand as flown

AuxiliaryData

RemarkAvailabilityTypeContentDataProducts

7. SUMMARY

The TET-1 mission is a national program funded from

the German Space Agency. The TET program started

with Phase A in January 2005, which ended October

2006. The TET-1 Phase B started in June 2007,

followed by a successful SRR in August 2007 and was

completed after the PDR beginning 2008. With PhaseC/D Kick-off in May 2008 and the launch date mid of

2010 not only the satellite has to be ready within two

years also the ground segment and the launch segment.

The goal of TET is the support of German industry and

research institutes with the on-orbit verification of new

and innovative satellite technologies. For this purpose

regular and reliable flight opportunities shall be offered,

which can be realized on short notice. TET shall provide

the required verification platform and shall be based on

a satellite bus which was qualified on orbit during the

BIRD mission.

The launch of the first satellite, TET-1, is scheduled formid 2010. In total, eleven different payloads were

selected to be demonstrated on TET-1. These include

optical experiments such as an infrared camera as well

as novel solar cells, batteries, on-board computers, GPS

receivers and a propulsion system.

After the LEOP and commissioning phase, the one year

mission operation will begin. Payload data will be

transmitted to the TET ground segment and provided to

the experimenters via the Payload Data Center.

8. REFERENCES

1. E. Lorenz and H. Jahn, BIRD: more than 3 years

experience in orbit; Small satellites for Earth

Observation, Selected Proceedings of the 5th

International symposium of the International

Academy of Astronomics, 102-109 (2005)

2. Sergio Montenegro and Felix Holzky:

BOSS/EVERCONTROL OS/Middleware Target

ultra high Dependability; DASIA2005, 30th May –

2nd June 2005 Edinburgh, Scotland

3. Z. Yoon, T. Terzibaschian, C. Raschke: OptimalThree-Axis Attitude Control Design, Simulation

and Experimental Verification for Small Satellites

Using Magnetic Actuators; Small Satellites

Systems and Services - The 4S Symposium; 26-30

May 2008

4. S. Roemer, T. Terzibaschian, A. Wiener, W.

Bärwald: Expertises with the BIRD ACS test

facility and the resulting design of a state of the art

mini- and micro-satellite ACS test facility; 6th IAA

Symposium on Small Satellites for Earth

Observation; 23th - 26th April 2007

Documents

4S_Paper_TET_Rhodos_080526